This invention relates generally to the manufacture of dimensioned lumber from sawn cants and more particularly to the orientation of sawn cants for edging operations.
In the manufacture of dimensioned lumber from trees, the tree is initially sawn with a series of longitudinally extending parallel cuts to divide the tree into cants. The resulting cants have opposed sawn faces parallel to each other with irregularly shaped wanes along opposite side edges of the cant. To form the cant into dimensioned lumber, it is necessary that these wanes be removed with edgers.
In typical edging operations, the cant is fed through the edger along a straight edging path with the edger making spaced apart cuts on opposite side edges of the cant parallel to the edging path to remove the wanes. The spacing between these parallel cuts is such that all of the wane is removed and the resulting lumber has a standard width. Because the wanes along opposite side edges of the cant have an irregular shape, the orientation of the cant with respect to the edging path affects the usable lumber yield from the cant after it has been edged. Therefore, it is necessary to orient the cant with respect to the edging path prior to entry of the cant into the edger to insure that all of the wane will be removed while at the same time the lumber yield from the cant will be maximized.
One prior art technique which has been used to orient the cant on the infeed unit uses a manually controlled orientation device on the infeed unit with which the operator orients the cant on the infeed unit after the cant has been fed thereonto. One of the problems associated with this prior art technique is that the operator must wait until the previously oriented cant has cleared the infeed unit before the next cant can be fed onto the infeed unit and then oriented. A significant amount of time is lost because the operator must wait until the cant is fed onto the infeed unit for orientation.
Another prior art technique which has been used to orient the cant on the infeed unit involves the use of an optical scanning device which scans the cant as to its size and shape and supplies the scanned information to a computer. The computer then determines the desired orientation of the cant with respect to the edging path to maximize the lumber yield from the cant and causes the cant to be oriented on the infeed unit using adjustable stops so that the cant has the desired orientation with respect to the edging path. While the technique of optically scanning the cant does have the capability of orienting the cant for maximum lumber yield and for operating sufficiently fast to minimize the time the cant is maintained on the infeed unit, the initial cost of such prior art systems has been sufficiently high that such systems have remained economically unfeasible except in very high speed edging operations. Moreover, because these prior art optical scanning systems have typically been unable to handle all possible cant configurations, an operator was still required to monitor the optical scanning system in order to orient those cants which could not be handled by the optical scanning system.